Method for the purification of titanium tetrachloride



Patented Feb. 18, 1947 METHOD FOR THE PURIFICATION OF TITANIUMTETRACHLORIDE Walter F. Meister, Elizabeth, N. J assignor to NationalLead Company, New York, N. Y., a corporation of New Jersey .No Drawing.Application March 30, 1945, Serial No. 585,812

4 Claims.

This invention relates to the purification of titanium tetrachloride.

This application is a continuation-in-part of co-pending application,Serial No. 457,971, filed September 11, 1942.

Titanium tetrachloride in its pure form is a water-white liquid. Thecommercial products, however, which are obtained by chlorination ofvarious available titaniferous materials, such as rutile or residuesobtained from the extraction of iron from titaniferous iron ores or oftitaniferous iron ores, themselves, are invariably contaminated withimpurities which are carried over with the titanium chloride vaporsduring the chlorination process. The crude condensate of titaniumtetrachloride usually has a strong yellowish color;

The magnitude and type of contaminants which will be found in thecondensed vapors from the chlorination operation will depend upon thepurity of the titaniferous material used and the method of chlorination.

, A study of the chlorides of the elements of the various groups of theperiodic system reveals that there are a number of elements besidestitanium which may be reacted with chlorine to form volatil chlorideswhich will be carried over with the titanium tetrachloride vapors duringthe chlorination operation. Some of these chlorides may be more or lesseasily separated from the titanium tetrachloride condensate; those thatare in solid form at ordinary temperatures and insoluble in thetetrachloride by settling and filtration, or both, and those which aremiscible with the tetrachlorid by fractional distillation. However, aseparation of solid chlorides from titanium tetrachloride seldom efiectscomplete removal of the chlorides and depending upon the solubility ofthe respective chlorides they will be found in varying amounts asimpurities in the titanium tetrachloride. Such impurities are notreadily eliminated by distillation treatments because they tend to carryover with the vapors of titanium tetrachloride. Furthermore, fractionaldistillation to remove miscible chlorides is not completely satisfactorybecause depending upon the vapor pressure of the respective chloridesthey will tend to distil over with the titanium tetrachloride and befound in the condensate. One such chloride which, because of theproximity of its boiling point to that of titanium tetrachloride, cannotbe separated by fractional distillation is vanadium chloride. Among thechlorides of other elements which tend to distil over with the titaniumtetrachloride may be mentioned those of silicon, phosphorus, antimonyand sulfur. Many of the contaminating chlorides which, for the foregoingreasons, may be found in titanium tetrachloride, impart discoloration.This is particularly true of vanadium tetrachloride.

That the discoloring impurities cannot be eliminated from titaniumtetrachloride by straight fractional distillation is well known, andvarious treatments for the elimination of such impurities, includingvanadium have been proposed in the prior art. Thus, purification oftitanium tetrachloride has been carried out by treatment with certainmetals alone, such as iron in powder form or with sodium amalgam priorto distillation. It has, however, been found that such treatments arenot entirely satisfactory, repeated treatments and distillations beingnecessary for a substantially complete removal of these impurities.

Other purifying treatments for titanium tetrachloride, such as withdiand trichloride of titanium, activated carbon, activated inorganiccompounds such as alumina, silica, or titanium dioxide, and certainorganic compounds capable of polymerization have recently been disclosedin the art.

It has now been discovered, according to the present invention, thatimpure titanium tetrachloride may be decolorized and purified in a;single distillation operation to form a pure, waterwhite condensate bycontacting the impure liquid with small amounts of alkali metalhydroxide, certain powdered metals and water.

Accordingly, it is among the objects of the present invention to producein a single distillation a clear water-white, pure titaniumtetrachloride. Other objects will be apparent from the follow ingdescription.

According to the present invention, the impure titanium tetrachloride ismixed with a small amount of alkali metal hydroxide, e. g., sodium,potassium or lithium hydroxide, a small amount of a finely-divided metalpreferably as a powder, e. g.., iron, zinc, tin, copper and antimony,and a small amount of water. The mixture is heated under a refluxcondenser at normal pressure. After suflicient time has elapsed for thetreatment to take effect, the titanium tetrachloride is recovered by asingle distillation. The distilled liquid i water-white and free ofimpurities.

In order to facilitate the operation, mechanical agitation may beemployed, or dry, inert gases may be bubbled through the liquid duringthe treatment and subsequent distillation. Suspended and colloidalmatter and dissolved gases which have not otherwise been removed shouldpreferably be substantially eliminated by, for example, a fractionaldistillation prior to the treatment with alkali metal hydroxide,powdered metal and water. Because of the reactivity of titaniumtetrachloride vapors with water, it is preferable to carry out thedistillation in a dry atmosphere.

If so desired, my novel treatment may be carried out under more thanatmospheric pressure.

' In that case, gaseous reaction products should preferably beeliminated prior to the application of pressure.

The time and temperature required for the treatment with the alkalimetalhydroxide, pownadium calculated on the TiOzbasis were placed inseven separate glass distillation apparatus and refluxed at about 136 C.in contact with alkali metal hydroxide, powdered metal and water, therespective metals and amounts used being shown in Table I, thendistilled at normal pressure out of contact with objects other thanglass and away from contact with the outside atmosphere.

The distillates were tested for vanadium the color of the distillate wasnoted.

The following Table I contains the results obtalned.

Table 1' and Alkali metal hydroxide, parts 1 Content of I vanadium indistillate calculated on T101, per cent Powdered r netal,

parts Color of distillate 1.0 (NaOH)- morn-- I Water-white l By weightor. the basis of 212.5 parts of crude TiCh. N. B.ln all sevenoxpcrinwnts, except No. 4, 0.2 part by Weight of water were present.

dered metal, and water depends upon the amount of impurities present inthe liquid and the amount of treating agents used. Ordinarily whencontacting the crude titanium tetrachloride with the treating mixture ofalkali metal hydroxide, powdered metal and water at or about thetemperature of boiling, i. e., about 136 C., a treatment time of fromabout one hour to about six hours is suflicient with an amount oftreating mixture equal to about 4 to about 10 grams of alkali metalhydroxide, about 3 to about grams of powdered metal and about 1 to about5 grams of water per liter of titanium tetrachloride. The alkali metalhydroxide may be added as such or it may be dissolved in the water to beused in the treatment and. used in the form of a concentrated aqueoussolution. The treatment of this invention is very II. EXAMPLES SHOWINGEFFICACY or COPPER AND ANTIMONY Two portions of discolored commercialtitanium tetrachloride containing 0.25 per cent vanadium calculated onthe T102 basis were placed in two separate glass distillation apparatusand refluxed at about 136 C. in contact with alkali metal hydroxide,powdered metal and water, the respective metals and amounts used beingshown in Table I, then distilled at normal pressure out of contact withobjects other than glass and away from contact with the outsideatmosphere.

The distillates were tested for vanadiumand the color of the distillatewas noted.

The following Table II contains the results obtained.

Table II R n Contgnt of Alkali metal Powdered uxmg e &2 hydrlotiride,meta 1 E21 6: Color of distillate 3 3235323? pa 5 parts hours on TiOa,per cent 1 0.76 (NaOH) 2.0 Sb. 4 Water-white 002 2 0.76 (N8OH)- 2.0 CUd0 002 By weight on basis of 174 parts of crude T1014. N. B.l.n bothexperiments 0.76 part by weight of water was present.

eilicient, and a recovery of more than 95 per cent of the titaniumtetrachloride is attained in the single treatment and distillation.

The residue containing the impurities which have been removed from thetetrachloride may be treated for the recovery of possible remainingtitanium tetrachloride and residual values, S'lCh as those ofnondistillable titanium compounds and other impurities, e. g., vanadium.

Having in the foregoing broadly described my invention, I shall nowproceed further to illustrate its working with the aid of actualexamples.

I. Exunmns Snowmc ErrrcacY or Icon, Zmc

, AND Tm Seven portions of discolored commercial titanium tetrachloridecontaining 0.15 per cent va- The invention has in the foregoing been de-60 scribed in connection with certain details of opride, which comprisesadmixing with crude ti.

tanium tetrachloride small amounts of an alkali metal hydroxide,selected from the group consisting of sodium, potassium and lithiumhydroxides, a finely-divided metal selected from the group consisting ofzinc, iron, tin, antimony, and

copper, and water, boiling the mixture under reflux conditions and thendistilling the so-treated titanium tetrachloride.

2. Method for purifying titanium tetrachloride, which comprises admixingwith crude titanium tetrachloride small amounts of an alkali metalhydroxide, selected from the group consisting of sodium potassium andlithium hydroxides, a finely-divided metal selected from the groupconsisting of zinc, iron, tin, antimony, and copper, and water, thealkali metal hydroxide being between about 4 to about 10 grams, thefinelydivided metal being between about 3 to about 20 grams and thewater being between about 1 gram to about 5 grams, per liter of titaniumtetraand water, the alkali metal hydroxide being between about 4 toabout 10 grams, the finelydivided metal being between about 3 to about20 grams and the water being between about 1 gram to about 5 grams, perliter of titanium tetrachloride, boiling the mixture under refluxconditions between about 1 hour and about 6 hours and then distillingthe so-treated titanium tetrachloride.

4. Method for purifying titanium tetrachloride, which comprises admixingwith crude titanium tetrachloride small amounts of sodium hydroxide,finely-divided iron metal and water, the sodium hydroxide being betweenabout 4 to about 10 grams, the finely-divided iron metal being betweenabout 3 to about 20 grams and the water being between about 1 gram toabout 5 grams, per liter of titanium tetrachloride, boiling the mixtureunder reflux conditions between about 1 hour and about 6 hours and thendistilling the so-treated titanium tetrachloride.

WALTER F. MEISTER.

REFERENCES CITED The following references are of record in the file ofthis patent:

Mellor, "Inorganic 8; Theoretical Chemistry," vol. 7, pages 78 and 79,1927.

Pamfllov, et al., The Chemistry of Titanium, Chemical Abstracts, vol.31, pages 4609-10.

